Inflatable contact member for electric switch



Feb. 21, 1967- 3,305,652

INFLATABLE CONTACT MEMBER FOR ELECTRIC SWITCH C. R. RADLOFF ETAL Filed June 4, 1965 JZQ/ f INVENTORS @ar/ 1? Fad/off 5 BY K 3! Jazz/2:222

HTTORNEY C OMPR E SSED AIR United States Patent 3,305,652 INFLATABLE CUNTACT MEMBER FOR ELECTRIC SWITCH Carl R. Radlotr", Grand Rapids, and Karl Sarafian,

Lathrup Village, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 4, 1965, Ser. No. 461,271 7 Claims. (Cl. 20083) This invention concerns an electric switch more and more particularly a contact assembly for an electric switch having unique applicability with high power electrical equipment such as dielectric embossing presses.

In our copending patent application Serial No. 358,825, filed April 10, 1964, entitled Electric Switch and assigned to the assignee of this invention, we disclose a switch construction having stationary and movable contact members, one of which includes a pair of spaced parallel blades. The other of the contact members has a flexible contact element which is electrically and mechanically connected to the contact member so as to form a cavity which in cross section is completely enclosed. The cavity is filled with a resilient material such as rubber and means are provided for moving the movable contact member into frictional engagement with the stationary contact member so that the flexible contact element engages the blades and is deformed against the resilient means to increase the effective contact area between the contact members.

The above-described switch has been found to be particularly useful in any circuit where large currents are carried and the contact blades of the switch are of an extended length. In such cases, any irregularities occurring in the blades can be compensated for through the deforming action on the flexible contact member and therefore good electrical contact is assured the full extent of the engaging parts of the switch so that the problem of arcing and welding is eliminated.

Although the above-described switch construction has been found to be satisfactory in use, the repeated rubbing action that occurs between the contact surfaces during the making and breaking of an electric circuit has caused at least one of the contact members to experience detrimental wear in a relatively short time.

The present invention contemplates an improved electric switch construction of the above-described type which alleviates the wear problem explained above by utilizing an inflatable flexible element that is incorporated with one of the contact members of the switch. More specifically, the present switch comprises a contact member which has a flexible contact element formed in the shape of a loop which encloses an inflatable rubber tube. Means are provided for selectively inflating and deflating the tube and include a source of compressed air and a control valve. In the normal position of the switch contact elements, the flexible element is located adjacent a rigid contact surface so that upon inflating the tube the flexible element is moved into engagement with the rigid contact surface and thereby establishes electrical contact therebetween.

A more complete understanding of this invention can be obtained from the following detailed description and the accompanying'drawings in which:

FIGURE 1 illustrates in block form a dielectric embossing press of the type with which the present invention can be incorporated;

FIGURE 2 is an enlarged sectional view taken on line 11 of FIGURE 1 and illustrates the shielding members incorporating an electric switch made in accordance with the invention;

FIGURE 3 is a perspective view with parts broken away showing the flexible contact portion of the switch in FIGURE 2;

FIGURE 4 is a modified form of the flexible contact portion of FIGURE 3; and

FIGURE 5 is another modified form of the flexible contact portion of FIGURE 3.

Referring now to FIGURE 1, a dielectric embossing press 10 is shown having an oscillator section 12 and a Work section 14 which includes upper and lower shielding sections 16 and 18 located in the positions assumed when the press is closed. As best seen in FIGURE 2, the respective shielding sections are located adjacent to an upper stationary electrode 20 and a lower movable electrode 22 which can be provided with a plurality of elongated embossing blades, one of which is indicated by the numeral 42. Although not shown, an air or hydraulic cylinder is connected to the lower electrode for moving the latter upwardly toward the upper electrode to close the press. Thus, assuming a sandwich of thermoplastic material to be embossed is located between the electrodes and the press is closed as described, a pressure can be imposed upon the materials during the heat cycle. Moreover, when the press is closed, the shielding sections 16 and 18 engage each other so as to complete the electric circuit. Reference is made to the aforementioned copending patent application for a more complete description of the electric circuit and the layout of shielding sections utilized with the dielectric embossing press of FIGURE 1.

Although not shown, the shielding section 18 consists of four straight metal sheet portions located in rectangular form so as to completely surround the lower electrode 22. The lower end of the shielding section 18 is mechanically and electrically connected to a support 26 which carries the electrode 22. As shown in FIGURE 2, the upper end 28 of the shielding section 18 terminates with a flexible contact portion 30 that constitutes one part of the electric switch made in accordance with the invention. More specifically, the contact portion 30 comprises a flexible braided conductor 32 which extends the full length of each straight part of the shielding section 18 and is looped about a coextensive elongated inflatable tube 34. The conductor 32 is preferably made from a plurality of braided wires of a low resistance metal such as copper and has the opposite ends 36 and 38 thereof rigidly secured to the shielding section 18 by a plurality of fasteners such as the screw and nut combination indicated by the numeral 49. As seen in FIGURE 1, the fasteners are provided at spaced intervals along the length of the shielding and serve to establish an electrical connection between the braided con-ductor 32 and the shielded section 18.

In the preferred form, shown in FIGURE 3, the tube 34 is constructed so it has an elliptical shape when inflated with a somewhat pointed leading edge and elongated side portions 42 and 44. In this manner, the conductor 32 is expanded laterally so as to have parallel contact surfaces 46 and 48, each of which has an effective height as indicated by the letter y.

The shielding section 16, which constitutes the station ary contact member of this switch, is formed in four straight sections about the upper electrode 20 in a rectangular fashion similar to the shielding section 18. As seen in FIGURE 2, the shielding section 16 is located in vertical alignment with the shielding section 18 and comprises a pair of elongated parallel metal blades 50 and 52 rigidly connected to a spacer 54 which in turn is bolted to the fixed upper portion of the press adjacent the electrode 20. The blades 50 and 52 are respectively provided with inner contact surfaces 56 and 58 which are spaced apart for accommodating the contact member 30. Thus when the press is closed, the contact member 30 moves from the position indicated by the phantom lines into the area between the blades. During such time, the tube 34 is deflated so that there is no rubbing contact between the blades or the flexible conductor 32. Thereafter, a valve 60 is opened so as to direct compressed air via conduit 61 from a source 62 to the tube 34 which results in the latter being inflated sufliciently to laterally press the contact surfaces 46 and'48 into engagement with the opposing surfaces 56 and 58 of the blades. Prior to opening the press, the valve 60 would be moved to another position which would close off the air to the tube 34 and simultaneously exhaust the air therefrom and thereby relieve the pressure between the contact surfaces.

From the above, it should be apparent that the abovedescribed switch provides a large contact surface between the contact elements and therefore lends itself well for use in circuits which carry large currents. Also, in cases Where the contact portions of the switch are of an extended length, any irregularities occurring between the spacing of the blades can be compensated for by the deforming action of the contact member and the inflatable tube. In addition to these two features, the most important advantage of this type of a switch construction is that wear of the conductor 32 is completely eliminated since there is no frictional rubbing between the contact surfaces when the press is being opened or closed.

FIGURE 4 shows a modified form of the invention which'differs from the configuration shown in FIGURES 2 and 3 primarily in that the tube 64 is formed in a U shape so as to have a pair of dependent legs 66 and 68 on opposite sides of the sheet portion 69. Thus, in-

creased rigidity is realized so as to preclude any tendency ofthe contact portion to be bent toward one side or the other.

FIGURE 5 shows another modified form which differs from the aforementioned switch constructions by having an inflatable tube 70 located on one side of the sheet portion 72 and a rubber filled tube 74 on the other. In this case, the sheet portion 72 would be bent slightly out of the vertical so that the'flexible contact member could be moved into an area between the blades without rubbing against the latter. Thereafter, by inflating the tube 70, the expansionof the latter would cause the braided conductor 76 to contact one of the blades and upon increased inflation, cause a flexing actionof the sheet portion or, in other words, a straightening movement thereof until the opposite contact surface engages the associated blade.

Various changes and modifications can be made in this construction without departing from the spirit of the invention. Such changes and modifications are contemplated by the inventors and they do not wish to be 1imited except by the scope of the appended-claims.

We claim:

1. An electric switch comprising stationary and movable contact members, one of said contact members having a flexible metallic contact element electrically connected thereto, said element being formed as a loop with the opposite ends thereof mechanically connected to the .associated contact member so as to form .a cavity which in cross section is completely enclosed, the other of said contact members having a rigid contact surface, inflatable means in said cavity, means for locating the flexible contact element in a position adjacent to the rigid contact surface, and a source of pressurized air for inflating the inflatable means so that the flexible contact element engages the rigid contact surface to provide electrical contact therebetween.

2. An electric switch comprising elongated stationary and movable contact members, one of said contact members having an elongated 'braided and metallic contact element electrically and mechanically connected to the associated contact member so as to form a cavity which in crosssection is completely enclosed, the other of said contact members having an elongated rigid contact surface, an inflatable rubber tube located in said cavity, means for locating the contact element in a position adjacent to the rigid contact surface, and a source of pressurized air for inflating said tube so that the contact element engages the rigid contact surface to provide electrical contact therebetween.

3. An electric switch comprising stationary and movable contact members, one of said contact members comprising a pair of spaced parallel blades, the other of said' contact members having a flexible braided and metallic element in the form ofa loop with the opposite ends electrically and mechanically connected to said other contact member, an inflatable rubber tube within said loop, means for moving the movable contact member into the space between said blades so that the flexible element is located between the blades, and means for inflating said tube whereby said contact surfaces are moved into electrical engagement with said blades.

4. An electric switch for a dielectric embossing press having vertically-spaced movable and stationary electrode members, firstand second elongated vertically aligned sheet-like conductor members enclosing the respective electrode members, each of said electrode members being electrically connected with the associated conductor member, one of said conductor members having a flexible metallic contact element electrically and mechanically connected thereto so as to form a cavity which in cross section is completely enclosed, the other of said conductor members having a rigid contactsurface, resilient means in said cavity, an inflatable tube in said cavity, means for moving said movable electrode member toward said stationary electrode member whereby the flexible contact element is located adjacent the rigid contact surface, and means for inflating said tube whereby said flexible contact element is moved into electrical engagement with the rigid contact surface.

5. An electric switch for a dielectric embossing press having vertically spaced movable and stationary electrode members, first and second elongated vertically aligned sheet-like conductor members enclosing the respective electrode members, each of said electrode members be.- ing electrically connected with the associated conductor members, one of said'conductor members terminating with a coextensive flexible metallic contact element, means electrically and mechanically connecting said element to said associated conductor member so as to form a cavity which in cross section is completely enclosed, the other of said conductor members terminating with parallel contact blades, aninflatable rubber tube in said cavity, means for moving said movable electrode mem ber toward said stationary electrode member whereby the flexible contact element is positioned between said contact blades, and a source of compressed air including a control valve for inflating said tube whereby said flexible contact element is moved into electrical engagement with said contact blades. 7

6. The switch of claim 5 whereinsaid tube takes the form of a U with the legs thereof located on the opposite side of the associated conductor member.

7. The switchof claim 5 wherein said tube is located on one side of the associated conductor and a filler of resilient material is located on the other side of said conductor.

References Cited by the Examiner UNITED STATES PATENTS 9/1941 Barbat 200-83 4/ 1966 Kizilos 20083 

1. AN ELECTRIC SWITCH COMPRISING STATIONARY AND MOVABLE CONTACT MEMBERS, ONE OF SAID CONTACT MEMBERS HAVING A FLEXIBLE METALLIC CONTACT ELEMENT ELECTRICALLY CONNECTED THERETO, SAID ELEMENT BEING FORMED AS A LOOP WITH THE OPPOSITE ENDS THEREOF MECHANICALLY CONNECTED TO THE ASSOCIATED CONTACT MEMBER SO AS TO FORM A CAVITY WHICH IN CROSS SECTION IS COMPLETELY ENCLOSED, THE OTHER OF SAID CONTACT MEMBERS HAVING A RIGID CONTACT SURFACE, INFLATABLE MEANS IN SAID CAVITY, MEANS FOR LOCATING THE FLEXIBLE CONTACT ELEMENT IN A POSITION ADJACENT TO THE RIGID CONTACT SURFACE, AND A SOURCE OF PRESSURIZED AIR FOR INFLATING THE INFLATABLE MEANS SO THAT THE FLEXIBLE CONTACT ELEMENT ENGAGES THE RIGID CONTACT SURFACE TO PROVIDE ELECTRICAL CONTACT THEREBETWEEN. 